U.S. patent number 7,532,796 [Application Number 11/540,980] was granted by the patent office on 2009-05-12 for fiber optic ribbons having one or more predetermined fracture regions.
This patent grant is currently assigned to Corning Cable Systems LLC. Invention is credited to David W. Chiasson.
United States Patent |
7,532,796 |
Chiasson |
May 12, 2009 |
Fiber optic ribbons having one or more predetermined fracture
regions
Abstract
A fiber optic ribbon having one or more fracture locations for
influencing the separation of the same at predetermined locations
is disclosed. The fiber optic ribbon includes a plurality of
optical fibers held together by a primary matrix. The primary
matrix includes a first fracture region for splitting the optical
fiber ribbon into a plurality of optical fiber subsets. The first
fracture region is defined by a first group of preferential tear
features that protrude beyond a major primary matrix plane, thereby
forming a first local minimum thickness between adjacent optical
fibers. The first local minimum thickness enables splitting of the
fiber optic ribbon into subsets at the first local minimum
thickness, thereby allowing the craft to separate the fiber optic
ribbon into subsets without using tools. Additionally, fiber optic
ribbons of the invention may include a secondary matrix.
Inventors: |
Chiasson; David W. (Edmonton,
CA) |
Assignee: |
Corning Cable Systems LLC
(Hickory, NC)
|
Family
ID: |
39271323 |
Appl.
No.: |
11/540,980 |
Filed: |
September 29, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080080822 A1 |
Apr 3, 2008 |
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Current U.S.
Class: |
385/114 |
Current CPC
Class: |
G02B
6/4404 (20130101) |
Current International
Class: |
G02B
6/44 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0843187 |
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WO |
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Other References
N Andrew Punch, Jr., Shail Moorjani, Steven T. Bissell, and Karen
E. Williams, Craft-Friendly 24-Fiber Ribbon Design, IWCS 1999, pp.
72-78. cited by other .
R.S. Wagman, G.A. Lochkovic, K.T. White, "Component Optimization
for Slotted Core Cables Using 8-Fiber Ribbons", IWCS 1995, pp.
472-478. cited by other .
Patent Cooperation Treaty, International Search Report for
PCT/US2007/20708, Mar. 19, 2008, 1 page. cited by other.
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Primary Examiner: Pak; Sung H
Assistant Examiner: Smith; Chad H
Attorney, Agent or Firm: Montgomery; C. Keith
Claims
That which is claimed:
1. A fiber optic ribbon having one or more fracture locations for
influencing a separation of the fiber optic ribbon at predetermined
locations, the fiber optic ribbon comprising: a plurality of
optical fibers; and a primary matrix, the primary matrix holding
all of the plurality of optical fibers together and contacting the
plurality of optical fibers, wherein the primary matrix has a first
fracture region for splitting the fiber optic ribbon into a
plurality of optical fiber subsets, the first fracture region is
defined by a first group of preferential tear features, the first
group of preferential tear features protruding beyond a major
primary matrix plane, thereby forming a first local minimum
thickness between adjacent optical fibers that enable splitting the
fiber optic ribbon into subsets at the first local minimum
thickness, wherein the major primary matrix plane is defined by an
exterior surface of the primary matrix, and wherein the fiber optic
ribbon further includes a secondary matrix material contacting an
exterior surface of the primary matrix.
2. The fiber optic ribbon of claim 1, wherein the first group of
preferential tear features protrude about 3 microns or more beyond
the major primary matrix plane.
3. The fiber optic ribbon of claim 1, wherein the first local
minimum thickness is less than a nominal thickness of the primary
matrix.
4. The fiber optic ribbon of claim 1, wherein the first group of
preferential tear features includes four protrusions.
5. The fiber optic ribbon of claim 4, wherein the four protrusions
are generally symmetrically disposed above the adjacent optical
fibers.
6. The fiber optic ribbon of claim 1, wherein the first group of
preferential tear features includes at least two protrusions.
7. The fiber optic ribbon of claim 1, wherein the first group of
preferential tear features includes at least two protrusions, the
two protrusions being disposed on opposite sides of the first local
minimum thickness.
8. The fiber optic ribbon of claim 1, wherein the fiber optic
ribbon includes a second group of preferential tear features,
thereby creating a second local minimum thickness for splitting the
fiber optic ribbon into subsets at the second local minimum
thickness, thereby providing preferential splitting of the fiber
optic ribbon into three optical fiber subsets.
9. The fiber optic ribbon of claim 1, wherein the subsets of the
fiber optic ribbon each include the same number of optical
fibers.
10. The fiber optic ribbon of claim 1, wherein the secondary matrix
has a secondary local minimum thickness of about 10 microns or
less.
11. The fiber optic ribbon of claim 1, wherein the fiber optic
ribbon is a portion of a fiber optic cable.
12. A fiber optic ribbon having one or more fracture locations for
influencing a separation of the fiber optic ribbon at predetermined
locations, the fiber optic ribbon comprising: a plurality of
optical fibers; and a primary matrix, the primary matrix holding
all of the plurality of optical fibers together and contacting the
plurality of optical fibers, wherein the primary matrix has a first
fracture region for splitting the fiber optic ribbon into a
plurality of optical fiber subsets, the first fracture region is
defined by a first group of preferential tear features, the first
group of preferential tear features being at least two protrusions
that extend beyond one of two major primary matrix planes, thereby
forming a first local minimum thickness between adjacent optical
fibers that enable splitting the fiber optic ribbon into subsets at
the first local minimum thickness, the at least two protrusions
being disposed on opposite sides of the first local minimum
thickness, wherein the one of the two major primary matrix planes
is defined by an exterior surface of the primary matrix, and
wherein the fiber optic ribbon further includes a secondary matrix
contacting an exterior surface of the primary matrix and the
secondary matrix has a secondary local minimum thickness of about
10 microns or less.
13. The fiber optic ribbon of claim 12, wherein the at least two
protrusions extend about 3 microns or more beyond the one of the
two major primary matrix planes.
14. The fiber optic ribbon of claim 12, wherein the first local
minimum thickness is less than a nominal thickness of the primary
matrix.
15. The fiber optic ribbon of claim 12, wherein the first group of
preferential tear features includes four protrusions.
16. The fiber optic ribbon of claim 15, wherein the four
protrusions are generally symmetrically disposed above the adjacent
optical fibers.
17. The fiber optic ribbon of claim 12, wherein the fiber optic
ribbon includes a second group of preferential tear features,
thereby creating a second local minimum thickness for splitting the
fiber optic ribbon into subsets at the second local minimum
thickness, thereby providing preferential splitting of the fiber
optic ribbon into three optical fiber subsets.
18. The fiber optic ribbon of claim 12, wherein the subsets of the
fiber optic ribbon each include the same number of optical
fibers.
19. The fiber optic ribbon of claim 12, wherein the fiber optic
ribbon is a portion of a fiber optic cable.
20. A fiber optic ribbon having one or more fracture locations for
influencing a separation of the fiber optic ribbon at predetermined
locations, the fiber optic ribbon comprising: a plurality of
optical fibers; a primary matrix, the primary matrix holding all of
the plurality of optical fibers together and contacting the
plurality of optical fibers, wherein the primary matrix has a first
fracture region for splitting the fiber optic ribbon into a
plurality of optical fiber subsets, the first fracture region is
defined by a first group of preferential tear features, the first
group of preferential tear features protruding beyond a major
primary matrix plane, thereby forming a first local minimum
thickness between adjacent optical fiber that enable splitting the
fiber optic ribbon into subsets at the first local minimum
thickness, wherein the major primary matrix plane is defined by an
exterior surface of the primary matrix; and a secondary matrix
contacting an exterior surface of the primary matrix.
21. The fiber optic ribbon of claim 20, wherein the secondary
matrix has a secondary local minimum thickness of about 10 microns
or less.
22. The fiber optic ribbon of claim 20, wherein the first group of
preferential tear features protrude about 3 microns or more beyond
the major primary matrix plane.
23. The fiber optic ribbon of claim 20, wherein the first local
minimum thickness is less than a nominal thickness of the primary
matrix.
24. The fiber optic ribbon of claim 20, wherein the first group of
preferential tear features includes four protrusions.
25. The fiber optic ribbon of claim 24, wherein the four
protrusions are generally symmetrically disposed above the adjacent
optical fibers.
26. The fiber optic ribbon of claim 20, wherein the first group of
preferential tear features includes at least two protrusions.
27. The fiber optic ribbon of claim 20, wherein the first group of
preferential tear features includes at least two protrusions, the
at least two protrusions being disposed on opposite sides of the
first local minimum thickness.
28. The fiber optic ribbon of claim 20, wherein the fiber optic
ribbon includes a second group of preferential tear features,
thereby creating a second local minimum thickness for splitting the
fiber optic ribbon into subsets at the second local minimum
thickness, thereby providing preferential splitting of the fiber
optic ribbon into three optical fiber subsets.
29. The fiber optic ribbon of claim 20, wherein the subsets of the
fiber optic ribbon each include the same number of optical
fibers.
30. The fiber optic ribbon of claim 20, wherein the fiber optic
ribbon is a portion of a fiber optic cable.
Description
FIELD OF THE INVENTION
The present invention relates generally to fiber optic ribbons.
More specifically, the present invention relates to fiber optic
ribbons having one or more fracture regions at predetermined
locations for splitting the fiber optic ribbon into subsets of
optical fibers.
BACKGROUND OF THE INVENTION
Fiber optic ribbons include optical waveguides such as optical
fibers that transmit optical signals, for example, voice, video,
and/or data information. Fiber optic cables using fiber optic
ribbons can result in a relatively high optical fiber-density.
Fiber optic ribbon configurations can be generally classified into
two general categories. Namely, fiber optic ribbons with subunits
and those without. A fiber optic ribbon with a subunit
configuration, for example, includes at least one optical fiber
surrounded by a primary matrix forming a first subunit, and a
second subunit having a similar construction (with its own discreet
primary matrix), which are connected and/or encapsulated by a
secondary matrix. On the other hand, fiber optic ribbons without
subunits generally have a plurality of optical fibers surrounded by
a single primary matrix material.
Optical fiber ribbons should not be confused with micro-cables
that, for example, have a strength member and a jacket. For
instance, U.S. Pat. No. 5,673,352 discloses a micro-cable having a
core structure and a jacket. The core structure requires that at
least one optical fiber is positioned between longitudinally
extending strength members, both of which are embedded in a buffer
material. The jacket of the '352 patent protects the core structure
and the material is selected to have good adhesion to the buffer
material and be abrasion resistant. Additionally, the strength
members are required to have a larger diameter than the diameter of
the optical fiber, thereby absorbing crushing forces that are
applied to the microcable.
On the other hand, optical fiber ribbons generally have a plurality
of adjacent optical fibers arranged in a generally planar array
forming a relatively high optical fiber density with a relatively
small cross-sectional footprint. Optical fiber ribbons without
subunits can present problems for the craft. For example, when
separating these optical fiber ribbons into a plurality of optical
fiber subsets, the craft must use expensive precision tools for
"cleanly" separating the optical fiber ribbon. Where the craft
elects to separate the optical fiber ribbon into subsets by hand,
or with a tool lacking adequate precision, stray optical fibers
and/or damage to the optical fibers can result. Stray optical
fibers can cause problems in optical ribbon connectorization,
organization, stripping, and splicing. Furthermore, damage to the
optical fibers is undesirable and can render the optical fiber
inoperable for its intended purpose.
However, there are fiber optic ribbon configurations that attempt
to aid the separation of fiber optic ribbons without using
subunits. For example, U.S. Pat. No. 5,982,968 requires an optical
fiber ribbon of uniform thickness having V-shaped stress
concentrations in the matrix material that extend along the
longitudinal axis of the fiber optic ribbon. V-shaped stress
concentrations can be located across from each other on the planar
surfaces of the fiber optic ribbon, thereby aiding the separation
of the fiber optic ribbon into a plurality of subsets. However, the
'968 patent requires a wider fiber optic ribbon because additional
matrix material is required adjacent to the optical fibers near the
V-shaped stress concentrations to avoid stray optical fibers after
separation. A wider ribbon requires more matrix material and
decreases the optical fiber density. Moreover, this wider spacing
complicates mass fusion splicing of the entire fiber optic ribbon.
Simply stated, the optical fibers of the wider ribbon do not have a
uniform spacing like a conventional fiber optic ribbon and, thus,
the spacing does not match the spacing for a conventional chuck of
the fusion splicer. Another embodiment of the '968 patent requires
applying a thin layer of a first matrix material around optical
fibers to improve geometry control such as planarity of the optical
fibers. Then V-shaped stress concentrations are formed in a second
matrix applied over the first matrix material, thereby allowing
separation of the subsets at the stress concentrations.
Another example of a separable fiber optic ribbon is described in
U.S. Pat. No. 5,970,196. More specifically, the '196 patent
requires a pair of removable sections positioned in V-shaped
notches located across from each other on opposite sides of the
planar surfaces of an optical fiber ribbon. The removable sections
are distinct from the primary matrix and are positioned between
adjacent interior optical fibers of the optical fiber ribbon to
facilitate the separation of the optical fiber ribbon into subsets
at the V-shaped notches. The removable sections can either be flush
with the planar surfaces of the optical fiber ribbon, or they may
protrude therefrom. These known fiber optic ribbons have several
disadvantages. For example, they can be more expensive and
difficult to manufacture because of the added complexity of the
distinct removable sections. Additionally, from an operability
standpoint, the V-shaped stress concentrations and/or V-shaped
notches can undesirably affect the robustness of the optical fiber
ribbon and/or induce microbending in the optical fibers.
Optical fiber ribbons having subunits can have several advantages,
for example, improved separation, and avoidance of stray fiber
occurrences. A conventional optical fiber ribbon 1 employing
subunits encapsulated in a secondary matrix is shown in FIG. 1. In
particular, optical fiber ribbon 1 includes a pair of conventional
subunits 2 having optical fibers 3 encapsulated in a primary matrix
5, which are then encapsulated in a secondary matrix 4. The
thickness T1 of primary matrix 5 is continuous and uniform.
Likewise, the thickness t1 of the secondary matrix 4 covering the
planar portions of subunits 2 is continuous and uniform. For
example, subunit 2 can include six 250 .mu.m optical fibers 3
disposed in primary matrix 5 having an overall uniform thickness T1
of 310 .mu.m and secondary matrix 4 has a thickness t1 of 10 .mu.m
for an overall fiber optic ribbon thickness T2 of 330 .mu.m.
However, conventional optical fiber ribbon 1 having subunits 2 has
disadvantages. For example, one concern is the potential formation
of wings W (FIG. 1) during hand separation of subunits 2. Wings W
can be caused by, for example, a lack of sufficient adhesion
between common matrix 4 and subunit matrix 5 and/or random
fracturing of the secondary matrix during separation. The existence
of wings W can negatively affect, for example, optical ribbon
organization, connectorization, stripping, and/or splicing
operations by the craft. Additionally, wings W can cause problems
with ribbon identification markings, or compatibility of the
subunit with ribbon handling tools, for example, thermal strippers,
splice chucks, and fusion splicers. Furthermore, the abutting
subunits can increase the spacing between the adjacent optical
fibers of the subunits. Thus, the spacing of the optical fibers of
the subunitized ribbon does not match the spacing for a
conventional chuck of the fusion splicer The present invention is
directed to optical fiber ribbons having one or more fracture
regions at predetermined locations for splitting the ribbon into
subsets of optical fibers while maintaining a uniform spacing for
the optical fibers.
SUMMARY OF THE INVENTION
The present invention is directed to fiber optic ribbons having one
or more fracture locations for influencing the separation of the
same at predetermined locations. The fiber optic ribbons include a
plurality of optical fibers held together by a primary matrix.
Moreover, the optical fibers of the ribbon have the same spacing as
a conventional ribbon and, thus, can be mass fusion spliced using
conventional splice chucks having a standard spacing. In one
embodiment, the primary matrix has a first fracture region for
splitting the optical fiber ribbon into a plurality of optical
fiber subsets. The first fracture region is defined by a first
group of preferential tear features, where the first group of
preferential tear features protrude beyond a major primary matrix
plane. The first group of preferential tear features form a first
local minimum thickness between adjacent optical fibers that enable
splitting the fiber optic ribbon into subsets at the first local
minimum thickness. Consequently, the craft can split the fiber
optic ribbon into subsets without using tools.
Another aspect of the present invention is directed to a fiber
optic ribbon having one or more fracture location for influencing
the separation of the same at predetermined locations. The primary
matrix of this ribbon has a first fracture region for splitting the
optical fiber ribbon into a plurality of optical fiber subsets. The
first fracture region is defined by a first group of preferential
tear features that includes at least two protrusions that extend
beyond one of two major primary matrix planes. The at least two
protrusions form a first local minimum thickness between adjacent
optical fibers that enable splitting the fiber optic ribbon into
subsets at the first local minimum thickness. Additionally, the at
least two protrusions are disposed on opposite sides of the first
local minimum thickness.
The present invention is also directed to a fiber optic ribbon
having one or more fracture locations for influencing the
separation of the fiber optic ribbon at predetermined locations.
The primary matrix has a first fracture region for splitting the
optical fiber ribbon into a plurality of optical fiber subsets
where the first fracture region is defined by a first group of
preferential tear features. The fiber optic ribbon further includes
a secondary matrix. The secondary matrix may form one or more
generally planar surfaces at the major planes of the fiber optic
ribbon.
It is to be understood that both the foregoing general description
and the following detailed description present embodiments of the
invention, and are intended to provide an overview or framework for
understanding the nature and character of the invention as it is
claimed. The accompanying drawings are included to provide a
further understanding of the invention, and are incorporated into
and constitute a part of this specification. The drawings
illustrate various embodiments of the invention, and together with
the description serve to explain principals and operations of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 depicts a cross-section of a conventional fiber optic ribbon
having subunits.
FIG. 2 is a cross-sectional view of a fiber optic ribbon according
to the present invention.
FIG. 3 is a partial enlarged view of the fiber optic ribbon of FIG.
2 showing the fracture region in greater detail.
FIG. 4 is a cross-sectional view of another fiber optic ribbon
according to the present invention.
FIG. 5 is a cross-sectional view of an explanatory fiber optic
ribbon according to the present invention.
FIGS. 6 and 7 are cross-sectional views of fiber optic cables
having fiber optic ribbons according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Reference will now be made in detail to the present preferred
embodiments of the invention, examples of which are illustrated in
the accompanying drawings. Whenever practical, same reference
numerals will be used throughout the drawings to refer to the same
or like parts. FIG. 2 depicts a cross-sectional view of a fiber
optic ribbon 20 according to the present invention. Fiber optic
ribbon 20 has at least one fracture location FR1 for influencing
the separation of a primary matrix 24 of the optical fiber ribbon
into a plurality of optical fiber subsets at a predetermined
location. Specifically, fiber optic ribbon 20 includes a plurality
of optical fibers 22 held together by primary matrix 24 in a
generally planar configuration forming an elongate structure with a
generally uniform spacing for optical fibers 22. Generally
speaking, optical fibers 22 are generally abutting, thereby
imparting an optical fiber spacing that matches a conventional
fusion splicing chuck. Primary matrix 24 generally contacts optical
fibers 22 and may encapsulate the same, thereby providing a robust
structure for processing and handling. Primary matrix 24 includes
first fracture region FR1 for splitting the optical fiber ribbon
into a first optical fiber subset SA and a second optical fiber
subset SB. First fracture region FR1 is defined by a first group of
preferential tear features 24a, 24b, 24c, 24d. Preferential tear
features 24a, 24b, 24c, 24d protrude beyond one of a plurality of
major primary matrix planes at a medial portion of the fiber optic
ribbon 20, thereby forming a first local minimum thickness T1 (see
FIG. 3) between adjacent optical fibers. First local minimum
thickness T1 enables reliable hand separation of fiber optic ribbon
20 into first subset SA and second subset SB at the first local
minimum thickness T1. More specifically, preferential tear features
24a and 24b protrude beyond a first major primary matrix plane PMP1
and preferential tear features 24c and 24d protrude beyond a second
major primary matrix plane PMP2, thereby creating a relatively
large primary matrix thickness gradient between interface optical
fibers 22I (i.e., a fourth and a fifth optical fiber of fiber optic
ribbon 20). This relatively large primary thickness gradient
influences the initiation the fracture of primary matrix 24 during
separation at the desired fracture location between interface
optical fibers 12I. Simply stated, fracture region FR1 includes a
valley disposed between the protrusions for influencing the
initiation of the primary matrix fracture between the interface
optical fibers.
As best shown in FIG. 3, first fracture region FR1 employes local
minimum thickness T1 that is less than a nominal thickness T2 of
fiber optic ribbon 20. Illustratively, local minimum thickness T1
is smaller than nominal thickness T2 by about 5 microns or more.
Nominal thickness T2 of the fiber optic ribbon is defined as the
thickness between the first major primary matrix plane PMP1 and the
second major primary matrix plane PMP2 of the fiber optic ribbon.
By way of example for explanatory purposes, optical fibers 22 may
have a nominal diameter of about 250 microns and nominal thickness
T2 of fiber optic ribbon is about 310 microns for generally
maintaining the planarity of optical fibers 22 and local minimum
thickness is about 230 microns. Additionally, preferential tear
features 24a,24b,24c,24d protrude beyond respective major primary
matrix planes PMP1 and PMP2 by about 3 microns or more, such as
about 5 microns, but may protrude up to 50 microns or more.
Consequently, the craft can easily and cleanly (i.e., inhibiting
the formation of wings in the primary matrix) separate fiber optic
ribbon 20 into subsets SA, SB by hand near local minimum thickness
T1 of primary matrix 24. Of course, the concepts of the present
invention are suitable for use with fiber optic ribbons having
other dimensions and/or structures.
Preferential tear features 24a,24b,24c,24d are shown as generally
convex profiles, but may have any suitable profile such as
rectangular or angular for creating the desired fracture region
and/or separation characteristics. Furthermore, the preferential
tear features have a maximum protrusion MP that is generally
disposed above an interface optical fiber 22I. In other words, a
line A-A drawn vertically through the maximum protrusion MP
intersects a portion of the interface optical fiber 22I. Simply
stated, preferential tear features may include any combination of
suitable shape, maximum protrusion MP, and/or local minimum
thickness T1 using the concepts of the invention that influences
the fracture of the primary matrix for separation into subsets.
Fiber optic ribbon 20 is advantageous since it allows a
conventional spacing among the optical fibers such as between the
interface optical fibers 22I (and the edge optical fibers), thereby
allowing mass fusion splicing of same using standard splice chucks
with the fusion splicer. Stated another way, optical fibers 12 of
fiber optic ribbon 20 can be positioned closely together (i.e.,
abutting arrangement) while still influencing the initiation of the
fracture of the primary matrix at a predetermined location during
hand separation. For instance, fiber optic ribbon 20 is configured
for hand splitting into two subsets each having four optical
fibers. Of course, fiber optic ribbons of the present invention
could have other suitable numbers of subsets and/or optical fibers
per subset.
The concepts of the present invention should not be confused with
conventional ribbons that may have undulations across their
cross-sectional surface due to manufacturing variations. These
undulations can cause variations in the conventional ribbon
thickness at random locations, rather than, for instance,
predetermined shapes. For example, the thickness of the
conventional ribbon can be 310.+-.3 microns at random locations
across the cross-section. On the other hand, ribbons according to
the present invention have fracture regions at predetermined medial
portions of the primary matrix for influencing fracture of the
primary matrix between interface optical fibers. Likewise, the
present invention should not be confused with fiber optic ribbons
that use subunits for providing separation since the fracture
regions of the present invention are disposed in the primary
matrix.
Fiber optic ribbons of the present invention are also advantageous
compared with fiber optic ribbons using subunits for other reasons.
For instance, the print statements on fiber optic ribbons of the
present invention may have less distortion. Typically, print
statements are placed on the primary matrix for durability purposes
(i.e., the print statement is covered by the secondary matrix
material and cannot be rubbed off). Consequently, fiber optic
ribbons having subunits place the print statement on two adjacent
subunits that are not yet connected by the secondary matrix, thus,
the print statement becomes distorted at the region between
subunits since the ink falls between the subunits. On the other
hand, the primary matrix of fiber optic ribbons of the present
invention is continuous, thereby providing a surface for the ink
and inhibiting distortion of the print statement.
Primary matrix 24 may be, for instance, a radiation curable
material or a polymeric material; however, other suitable materials
are possible. By way of example, one suitable UV curable material
is a polyurethane acrylate resin commercially available such as
sold under the tradename 950-706 by DSM Desotech, Inc. of Elgin,
Ill. Of course, other suitable UV materials are possible such as
polyester acrylate resins that are commercially available from
Borden Chemical, Inc. of Columbus, Ohio. As known, the degree of
cure (i.e., cross-link density) affects the mechanical
characteristics of the radiation curable material. For example, a
significantly cured material can be defined as one with a high
cross-link density for the material, which can be too brittle.
Further, an undercured material can be too soft and possibly have a
relatively high coefficient of friction (COF) that causes an
undesirable level of ribbon friction. The cured UV material has a
modulus in the range of about 50 MPa and about 1500 MPa depending
on the radiation dose. Different modulus values can provide varying
degrees of performance with respect to characteristics such as hand
separability and robustness of the ribbons. Additionally,
thermoplastic materials such as polypropylene are possible as a
matrix material.
Variations on the concepts of the present invention are possible.
For instance, FIG. 4 depicts a cross-sectional view of another
fiber optic ribbon 40 according to the present invention. Fiber
optic ribbon 40 is similar to fiber optic ribbon 20, but primary
matrix 42 includes a first fracture region FR1 and a second
fracture region FR2 and further includes a secondary matrix 45.
Using two fracture regions allows the craft to split fiber optic
ribbon 40 into three subsets SA, SB, and SC. More specifically,
fiber optic ribbon 40 includes twelve optical fibers 22 disposed in
primary matrix 42 and each of the subsets includes the same number
of optical fibers 22 (i.e., each subset SA, SB, and SC has four
optical fibers 22). Also, fiber optic ribbon 40 includes
protrusions (not numbered) adjacent the edge optical fibers 22e for
manufacturing control. In other words, having protrusions at the
far ends of primary matrix 42 aids in guiding the fiber optic
ribbon into secondary coating die. Of course, other optical fiber
ribbons can include any desirable number optical fibers, subsets,
and/or optical fibers per subset.
Fiber optic ribbon 40 also includes secondary matrix 45. As shown,
secondary matrix 45 imparts a generally planar surface for fiber
optic ribbon 40, thereby allowing for stacking of the fiber optic
ribbons for providing a dense array of optical fibers. Simply
stated, using a secondary matrix advantageously allows the
formation of relatively flat major surfaces of fiber optic ribbon
40 while still providing the desired separation characteristics.
Additionally, secondary matrix 45 has a plurality of minimum local
thicknesses T3 located adjacent to the fracture regions due to the
protrusions (not numbered) of the primary matrix. Local minimum
thickness T3 of secondary matrix 45 is about 10 microns or less,
but other suitable dimension are possible. Consequently, the
fracture of secondary matrix 45 initiates at this local minimum
thickness T3 of secondary matrix 45 and the forces applied during
separation are then directed to fracture region of the primary
matrix during hand separation.
Furthermore, fiber optic ribbons of the present invention can have
configurations for the fracture region that differ from those shown
in FIG. 2. By way of example, FIG. 5 depicts a cross-sectional view
of an explanatory fiber optic ribbon 50 according to the present
invention. More specifically, fiber optic ribbon 50 has a primary
matrix 54 including first fracture region FR1 and second fracture
region FR2 with different configurations, thereby allowing
separation into a plurality of subsets SA, SB, and SC. Stated
another way, fiber optic ribbon 50 has two groups of preferential
tear features, i.e., one group for each fracture region. As shown,
first fracture region FR1 of fiber optic ribbon 50 has two
protrusions 54a and 54b, instead of the four protrusions as
depicted in fiber optic ribbon 20. Protrusions 54a and 54b are
disposed on opposite sides of primary matrix 54 so that protrusion
54a extends beyond first major primary matrix plane PMP1 and
protrustion 54b extends beyond second major primary matrix plane
PMP2. Furthermore, first fracture region FR1 forms a local minimum
thickness (not labeled) between the fourth and fifth optical
fibers, which is smaller than a nominal thickness (not labeled) of
primary matrix 54. Like first fracture region FR1, second fracture
region FR2 of fiber optic ribbon includes two protrusions 54c and
54d. However, protrusions 54c and 54d of second fracture region FR2
are disposed on the same side of primary matrix 54 and they both
extend beyond first major primary matrix plane PMP1 as shown.
Additionally, second fracture region FR2 also forms a local minimum
thickness (not labeled) between the eighth and ninth optical
fibers, which is smaller than the nominal thickness of primary
matrix 54. Fiber optic ribbon 50 also includes a secondary matrix
55 for imparting generally flat major surfaces to fiber optic
ribbon 50.
Fiber optic ribbon of the present invention can, for example, be
used as a stand alone ribbon, a portion of a ribbon stack, or as a
portion of a fiber optic cable. Illustratively, FIG. 6 depicts a
cross-sectional view of an explanatory fiber optic cable having a
plurality of fiber optic ribbons 40 represented as solid lines.
Fiber optic cable 60 houses fiber optic ribbons 40 in a buffer tube
62 that may include a suitable filling material such as a grease,
gel, yarn, or one or more dry inserts. Filling materials are useful
for providing one or more functions such as cushion, coupling,
water-blocking, or the like. Fiber optic cable 60 also includes a
plurality of strength members 62 and a cable jacket 68. Of course,
fiber optic ribbons may be used in any suitable fiber optic cable.
FIG. 7 depicts a tubeless fiber optic cable 70 having a plurality
of fiber optic ribbons 40 according to the present invention. Fiber
optic cable 70 has a generally rectangular cavity for housing a
plurality of optical fiber ribbons 40 and may include one or more
filling materials. Strength members 74 provide tensile strength for
the cable and cable jacket 78 has a generally flat shape.
It will be apparent to those skilled in the art that various
modifications and variations can be made to the present invention
without departing from the spirit and scope of the invention. Thus
it is intended that the present invention cover the modifications
and variations of this invention provided they come within the
scope of the appended claims and their equivalents.
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